The present invention relates to a bone plating system and instrumentation used in the fixation of fractures of long bones such as the femur, tibia, humerus and radius, including periarticular fractures. More specifically, the present invention encompasses a bone plating system that aids in preoperative planning of plate selection and placement, intraoperative adjustment and fixation of the plate to the fractured bone, as well as implementation in minimally invasive surgery, hereinafter referred to as MIS.
Typical fixation of a fracture of a long bone with a bone plate requires making an incision in the tissue, reducing the fracture, placing a bone plate on the fractured bone, and securing the bone plate to the bone with fixation elements such as screws. The bone plate immobilizes the fracture and keeps the bone in a correct position so as to allow the fracture to heal.
Typically, bone plates have a bone contacting side and a side facing away from the bone with a plurality of holes or apertures extending between the two surfaces. These holes or apertures may be either threaded (for use with locking screws) or non-threaded (for use with regular screws) and may be circular or oblong in shape.
One such bone plate is shown in U.S. Pat. No. 6,623,486 in which the plate has a head portion for placement adjacent the metaphysis of the bone and a shaft portion for placement against the diaphysis of the bone. The plate includes both locking (threaded) holes and non-locking holes. The locking holes are adapted to receive bone screws with threaded heads or proximal areas which engage the threads in the locking holes to thereby lock the screw to the plate. Bone screws without threaded heads can be then inserted into the non-locking holes or into the oblong holes which oblong holes permit the screws to be oriented at various angles.
The non-threaded holes can accommodate threaded inserts which can couple the bone screws to the plate via the engagement of the outer bone screw threads with inner threads on the inserts. See, for example, U.S. Pat. No. 5,954,722. In addition, the bone plate holes can accommodate inserts adapted to receive cerclage wires. An example of such an insert is shown in U.S. Pat. No. 5,190,545.
One difficulty involved with the use of locking screws in minimally invasive, or other surgery, is that such a screw must be accurately aligned with the threaded hole in the plate upon insertion to prevent cross threading of the engaging threads. One way of achieving this alignment is by using guide wires such as Kirshner wires (K-wires) and locating them within the bone plate holes. Cannulated bone screws are then placed over the wires which, if accurately positioned, guide the threaded portion of the screw to engagement with the threaded plate hole in the proper alignment. Placement of the guide wires may thus become a critical aspect of the procedure.
As used herein, when referring to bones or other parts of the body, the term “proximal” means closer to the heart and the term “distal” means more distant from the heart. The term “inferior” means toward the feet and the term “superior” means towards the head. The term “anterior” means towards the front part of the body or the face and the term “posterior” means towards the back of the body. The term “medial” means toward the midline of the body and the term “lateral” means away from the midline of the body.
One of the difficulties involved with the implantation of a bone plate is determining the correct size of the bone plate to be used, as well as the position in which it is to be affixed to the bone. Commonly, a non-invasive scan of the fracture, such as an x-ray, will serve as the template by which a surgeon must select the appropriately sized bone plate, and determine where it should optimally be affixed to the bone. Based on this preoperative assessment, intraoperatively, the surgeon must then position the plate on the bone and affix it in the predetermined optimal position. Because the surgeon may only have the x-ray to refer to intraoperatively, the placement of the plate and the drilling of corresponding bone screw holes with correct trajectories for monoaxial screws leaves room for inaccuracy and less than optimal fixation.
Another difficulty involved with the implantation of a bone plate is holding and manipulating a long, slim plate in an incision during the implantation procedure.
Yet another issue with the implantation procedure is the size of the incision. Although it is known that tissue may be stretched, common incisions generally span the length of the bone plate to be implanted. This is because of the visualization that is required for proper alignment of the bone plate, as well as drilling of bone screw holes, and implantation of bone screws.
Since it is desirable to minimize scarring and disruption of blood supply to the muscles through the use of smaller incisions, as well as increase the speed and accuracy of surgical procedures, MIS techniques are becoming more popular. However, present implantation techniques, as described above, present challenges in terms of utilizing smaller incisions, providing faster operating times, and maintaining or improving ease of handing of bone plates, as well as accurately fixating them to bone. Thus, there is a need in the art for implants, instruments and methods that facilitate accomplishing these objectives.